/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
// copy code from Jackson xml TypeReference
package io.nop.core.type.utils;

import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;

/**
 * This generic abstract class is used for obtaining full generics type information by sub-classing; Class is based on
 * ideas from <a href="http://gafter.blogspot.com/2006/12/super-type-tokens.html"
 * >http://gafter.blogspot.com/2006/12/super-type-tokens.html</a>, Additional idea (from a suggestion made in comments
 * of the article) is to require bogus implementation of <code>Comparable</code> (any such generic interface would do,
 * as long as it forces a method with generic type to be implemented). to ensure that a Type argument is indeed given.
 * <p>
 * Usage is by sub-classing: here is one way to instantiate reference to generic type <code>List&lt;Integer&gt;</code>:
 *
 * <pre>
 * TypeReference ref = new TypeReference&lt;List&lt;Integer&gt;&gt;() {
 * };
 * </pre>
 */
public abstract class TypeReference<T> implements Comparable<TypeReference<T>> {
    protected final Type _type;

    protected TypeReference() {
        Type superClass = getClass().getGenericSuperclass();
        if (superClass instanceof Class<?>) { // sanity check, should never happen
            throw new IllegalArgumentException(
                    "Internal error: TypeReference constructed without actual type information");
        }
        /*
         * 22-Dec-2008, tatu: Not sure if this case is safe -- I suspect it is possible to make it fail? But let's deal
         * with specific case when we know an actual use case, and thereby suitable workarounds for valid case(s) and/or
         * error to throw on invalid one(s).
         */
        _type = ((ParameterizedType) superClass).getActualTypeArguments()[0];
    }

    public Type getType() {
        return _type;
    }

    /**
     * The only reason we define this method (and require implementation of <code>Comparable</code>) is to prevent
     * constructing a reference without type information.
     */
    @Override
    public int compareTo(TypeReference<T> o) {
        return 0;
    }
    // just need an implementation, not a good one... hence ^^^
}
